Containers for storing fluids such as liquids have been closed or sealed by employing various devices. For example, bottles, such as wine bottles, have been sealed by employing cylindrically shaped devices called corks. These devices, which are typically fabricated from cellulosic material, are compressed and placed into the opening of a bottle. Upon expansion of the cork, the bottle can be sealed thereby preventing the escape of fluid contained within the bottle.
In certain instances, it may be important to minimize or prevent the contamination of certain fluids stored within containers. For example, it is important to prevent medical fluids (e.g., medications or bodily fluids) from being contaminated or impacted by oxygen. Accordingly, it is highly advantageous to seal these containers with devices that prevent oxygen permeation into the container. As a result, corks or stoppers employed in conjunction with containers used in the medical industry often include natural or synthetic rubbers that exhibit low oxygen permeability.
Not only is contamination by oxygen is a concern, there is also a need in the industry, particularly in the medical industry, to allow for the addition and withdrawal of fluids from these containers. For example, as described in U.S. Pat. Nos. 6,840,510 and 5,232,109, a hypodermic needle or infusion spike is inserted through the stopper in order to add or withdraw fluid from the container. Upon removal of the hypodermic needle or infusion spike, the stopper advantageously reseals itself.
While both low oxygen permeability and curability (i.e., the ability to reseal after puncture) are important features for stopper devices, the ability to manufacture stopper devices by efficient and economic processing techniques is likewise important. Where natural or synthetic rubbers are employed to manufacture these devices, the fabrication techniques are often limited to rubber casting or thermosetting techniques. In other words, the rubber is cured within a mold and released from the mold after the curing process.
Thermoplastic elastomers include materials that exhibit many of the properties of thermoset elastomers yet are processable as thermoplastics. One type of thermoplastic elastomer is a thermoplastic vulcanizate, which includes fully cured or partially cured rubber within a thermoplastic matrix. Thermoplastic vulcanizates are conventionally produced by dynamic vulcanization, which includes a process whereby a rubber can be cured or vulcanized within a blend with thermoplastic resin while the polymers are undergoing mixing or masticating at some elevated temperature, preferably above the melt temperature of the thermoplastic resin. For example, WO 01/10950 teaches thermoplastic vulcanizates that include a thermoplastic polyurethane having one major glass transition temperature of less than 60° C. and an a polar rubber. The a polar rubber may include butadiene rubber, styrene-butadiene rubber, isoprene rubber, natural rubber, butyl rubber, ethylene-propylene rubber, ethylene-propylene-diene monomer rubber, or others. The thermoplastic vulcanizate may also include other constituents commonly employed in the art including extender oils.
Despite the fact that thermoplastic elastomers, particularly thermoplastic vulcanizates, have been known for many years, and the need for useful stoppers, particularly for the medical industry, has existed for many years, technologically useful stoppers prepared from thermoplastic vulcanizates do not exist in the prior art. Inasmuch as thermoplastic vulcanizates provide an efficient and economical route to the preparation of stoppers, the ability to fabricate stoppers from plastic vulcanizate would be desirable.